1. Field of the Invention
This invention relates to vectorable exhaust nozzles and particularly to a new and improved exhaust nozzle which is effective for providing thrust vectoring in the pitch and yaw directions.
2. Description of the Prior Art
Aircraft designers and particularly those designing high speed highly maneuverable military aircraft are constantly seeking better ways for controlling the aircraft and increasing its maneuverability in flight. The improvements are needed for anti-aircraft missle avoidance and other combat maneuvers. Additionally aircraft designers are trying to improve short take off and landing capabilities of aircraft. Exhaust systems, particularly for modern, high speed, military aircraft, have been adapted to provide a high degree of maneuverability over a wide variety of flight conditions including altitude, speed and Mach number while maintaining cruise efficiency.
Aircraft maneuverability may be provided by aircraft control surfaces such as wing flaps or ailerons or rudders. These means however are somewhat limited in their effectiveness because of large differences in operational flight conditions such as air speed. Thrust vectoring nozzles, though often more complicated, are more effective because they allow large thrust loads to be quickly applied in the pitch and yaw direction of the aircraft thereby providing the aircraft with enhanced maneuverability which is relatively independent of air speed.
In addition to flight maneuverability aircraft designers wish to optimize cruise efficiency which can be achieved through the use of a variable geometry exhaust nozzle on the gas turbine engine. A variable geometry nozzle permits the size of the nozzle's throat and the nozzle's exit to be changed in response to changes in flight conditions, such as air speed and altitude. Most exhaust nozzles for high speed aircraft employ a converging diverging exhaust nozzle. Converging diverging nozzles are well known in the field and generally means that the cross-sectional area of the exhaust nozzle in a downstream direction decreases to a position of minimum area, called the throat, and then increases to the downstream end or exit of the nozzle. Exhaust nozzles are often made variable through the use of a plurality of moveable nozzle sections in order to get a desired throat and exit areas. Nozzles capable of controlling the size of throat and exit are conventionally referred to as variable nozzles. Two dimensional convergent divergent nozzles are preferred because of the ease with which they can effect pitch control using the same positionable or variable flaps employed to maintain a desired throat and exit areas.
Current vectorable exhaust nozzle designs are limited as to the effectiveness of the thrust in the yaw direction. Though pitch can be effected by two dimensional flap control yaw is very difficult to provide in such a design. Suggested means for providing thrust vectoring of two-dimensional nozzles in the yaw direction include gimbaling the entire nozzle or pivoting split flaps in an axisymmetric manner to provide an aircraft pivoting moment. Such means have several drawbacks such as limited effectiveness, weight penalties and complexity, due to structural, kinematic, or aerodynamic constraints. Greater degrees of pivotal movement can be achieved by combining flaps with a gimbaled nozzle. However, such nozzles generally require complicated hardware and controls and are thus expensive and heavy.
In addition to the complexity of multi-directional vectored thrust nozzles there are problems integrating the nozzle with the aircraft. This in turn interferes with the nozzles operation and performance and also with the performance of the aircraft. In view of the above-mentioned problems, it is, therefore, an object of the present invention to provide gas turbine engines with improved means of vectoring the exhaust gas flow or thrust of an aircraft gas turbine engine.
It is another object of the present invention to provide a pitch vectorable nozzle with means of yaw vectoring.
Yet another object of the present invention to provide a pitch vectorable nozzle with means of yaw vectoring that does not significantly interfere with or adversely effect the performance of the aircraft, its gas turbine engine, or the engine's vectorable nozzle.
Another object of the present invention is to provide a variable geometry exhaust nozzle with thrust vectoring capability in the yaw direction.
Another object of the present invention is to provide a variable geometry pitch vectorable exhaust nozzle with pitch and yaw capability which is compact, simple in structure, and light weight.
One more object of the present invention is to provide a variable geometry pitch vectorable exhaust nozzle having yaw capability which is easily integrated into an aircraft.
Yet another object of the present invention is to provide a two dimensional convergent divergent (2DCD) variable geometry pitch vectorable exhaust nozzle with yaw capability.